Inventions relating to the current subject matter have progressed since the mid 1940s. Since that time the inventor of the current invention has been active in this art and has designed and patented numerous mechanisms to eliminate slack between king pin of trailers and fifth wheel locking mechanisms. His experience with fifth wheels began during World War II when the military conducted studies of fifth wheel designs at the U.S. Government Ordinance and Engineering Department at Fort Belvoir and Aberdeen Maryland Proving Grounds. That testing led to the observation that the Government specifications for fifth wheels would allow wearing between king pins and locking mechanisms to such a degree that the slack created from such wearing caused damage to the drive train of the tractor and breakage of fifth wheel components which were, at that time, primarily steel castings.
For the most part, the trucking industry, as it has evolved since the 1940s, has relied on conventional fifth wheel designs for locking onto and supporting tractor trailer king pins. Such designs have incorporated features such as non-retracting lock release handles when the lock is in an open position, spring operated locking jaws, wedges and locking jaws opening on the rearward side of the fifth wheel hub, and wedge/jaw timers. Notwithstanding advances in fifth wheel designs such as those by the current inventor as described in U.S. Pat. Nos. 2,456,826, 3,844,584, 5,456,484 and 5,516,138, herein incorporated by reference, there is still a need to address and solve problems which remain inherently in fifth wheel/king pin coupling due to the forces of tremendous weight and leverage place on the locking mechanism and king pin while the tractor and trailer are engaged.
The inherent problems arise due to wear that increases tolerances between the king pin and locking mechanism. In some instances it has been found, notwithstanding measures designed to keep locking mechanism's elements in place, that the locking elements will slip from a fully locked position towards an unlocked position. Such movement caused by the king pin (i.e. squirting), forces the operating handle (lever arm) to move towards the open position with such force that a clicking or banging is noticeable by the tractor operator. Moreover, such force (squirting) may cause the jaw and wedge to jam in a partial open condition.
Some causes of slack and wearing have been addressed by inventions of the inventor such as disclosed in U.S. Pat. No. 2,726,878 in which the timing of the engagement of the lock jaw and wedge was designed to allow proper coupling of the lock jaw and wedge. In addition to incorporation of the timer, the lockjaw and wedge included angled wedge/jaw contact to allow for adjustment for wear when the wedge moved into locking position.
The design disclosed in the "878" patent has influenced the designs of other fifth wheel manufacturers in their effort to eliminate slack in the locking mechanism and was additionally the prime reason for the inventor's fifth wheel company becoming number one in the industry. Although the design of the 878 patent proved adequate over many years, the fact that the top contact plate between the fifth wheel and trailer was coated with grease allowed for such grease to seep down into the wedge and locking jaw elements. The presence of grease on these components causes the wedge and jaw to slip under the pressure of the king pin thereby causing such components to favor movement toward the open position and cause squirting of the wedge. The combination of wear between the jaw and wedge induced by normal operation of the fifth wheel and wear caused by squirting caused increases in tolerances with respect to the wedge, jaw, and king pin.
The issue of eliminating undesirable tolerance increases has been addressed in prior work of the inventor. U.S. Pat. No. 3,844,584 describes a jaw and wedge having a stepped mating surface the design of which was intended to eliminate sliding forces between the jaw and wedge caused by force applied due to the trailer king pin. The stepped design was contemplated to eliminate movement between the locking jaw and wedge by the presence of surfaces perpendicular to the force applied by the king pin. However, the stepped design has failed to solve the squirting problem because of three reasons. First, upon repetitive locking and unlocking the mechanism, the sliding action of the wedge in contact with the jaw causes the steps to wear down due to uneven sliding contact. This wearing causes the stepped contact surface areas to decrease with usage (approximately a two year period) thereby allowing the force applied by the king pin to generate squirting. Second, it is nearly impossible to keep heavy grease applied to the upper surface of the fifth wheel from seeping into the locking mechanism's wedge and jaw. The presence of such grease causes the wedge and jaw to tend towards slipping towards an unlocked position due to the reduction of friction between the wedge and jaw contact surfaces thus facilitating further wearing down of the stepped surfaces and promotion of squirting. Third, the wedge and jaw, being engaged towards the closed position primarily by coil spring force and a tolerance allowance of lateral movement of the lever arm toward an open position of about two inches when worn, inherently create "play" in the locked mechanism having a stepped wedge and jaw as well as virtually all prior described fifth wheel arrangements having a sliding wedge and jaw arrangement.
Other inventions respecting fifth wheel designs by the inventor have contemplated use of stepped arrangements associated with the wedge. In inventor's U.S. Pat. No. 3,318,616, a fifth wheel design is disclosed wherein a locking jaw of a rotating hook design is urged to remain in locking position by a wedge. Associated with the wedge is a pivoting locking dog having a detent which may be engaged with a rack carried by a frame portion of the fifth wheel. Although the locking dog was intended to maintain the position of the wedge, pressure from the king pin caused the urging of the locking jaw towards the open position whereby a maximum of pressure force was generated on the wedge which in turn applied force directly on the detent. In some instances the force applied to the locking dog and its detent was great enough to cause jamming of the detent in its engagement with the rack thereby making opening the locked mechanism problematic. Although the rack and detent arrangement of the "616" patent looks similar to the current invention, such earlier concept had no relation to the functionality or purpose contemplated in the present invention. The prior use of a rack and locking dog detent was for the purpose of only locking the king pin locking hook member and wedge in a closed position. Without such detent and rack no adequate means, except for the safety catch of the handle on the perimeter of the fifth wheel, could keep the rotating locking jaw from being urged in the open position.
Additionally, such design did not provide an auxiliary safety lock mechanism for the lever arm. Instead, the design required the addition of a safety lock at the perimeter of the fifth wheel which required the operator to release with one hand prior to pulling the handle with the other hand, which operation proved inconvenient as opposed to a direct pull on the handle with just one hand. Moreover, the 616 rack and detent design was integrally connected with the wedge and did not function to affect tolerances and did not incorporate the benefits of leverage allowed by the lever arm (which operates the opening and closing of the locking jaw and wedge) as is the case with the current invention's locking mechanism which uses sliding wedge and jaw members.
Still other inventions used in the trucking industry include safety catch members associated with the linear travel of non-retractable pull handles (i.e. the pull handle which is pulled outward from the fifth wheel by the operator to disengage the locking mechanism and which must remain extended outward and above the tractor tires when the locking mechanism is in the open position). In U.S. Pat. No. 5,641,174, a conventional fifth wheel is disclosed in which as much as two inches of play is allowed in the movement of the operating handle (lever arm) towards the open position before a safety catch is engaged. The problem with such single step safety catches is that large tolerances allowed by the movement of the operating handle before engagement of the safety catch allow for unacceptable slack to be generated promoting severe squirting. Moreover, the single position lock design, as disclosed in the "174" patent, may not allow proper engagement of the safety lock when the slack adjustment knock out rod is incorrectly adjusted by the operator. Further, the safety lock could fail to engage because the 174 design was subject to failure of the wedge and jaw properly locking where an auxiliary spring used in connection with the timer failed or was installed incorrectly. If the safety lock does not properly engage, severe squirting may generate enough force to push the lever arm towards the open position and if the safety lock is not properly engaged, there is the possibility of the lock releasing the king pin with potentially catastrophic consequences of the trailer becoming disengaged from the tractor.
Whereas the single step safety lock design of the invention described in the 174 patent will allow approximately two inches of lever arm movement at the safety lock when the wedge and jaw are worn, the current invention significantly avoids such play because the self-adjusting stepped design at the safety lock restricts the movement of the lever arm to one half inch maximum movement regardless of the condition of the jaw and wedge. Consequently, the current invention will restrict any banging effect whether or not the wedge is worn and further reduce significantly any force on the handle caused by fore and aft movement of the king pin.
A preferred embodiment of the current invention further allows the self-adjusting ratchet system to act as a safety lock. Moreover, the system is designed to follow a movement of the lever arm towards the closed position which self-adjustment will allow the wedge to compensate for a no less than one quarter inch lateral slack adjustment of the wedge for each step of adjustment in the system's ratchet rack. Whereas the 878 design could adjust the positioning of the wedge and jaw due to coil spring action, the 878 design could not prevent the occurrence of squirting caused by grease accumulation between the jaw and wedge because it had no inward self-adjusting ratchet catch system. Additionally, the invention disclosed in the 174 patent, as it has been produced and used in the field, could not make such an inherent adjustment due to the fact that the pull handle shaft was not long enough thereby causing the external hand grip of the pull handle to abut the outside perimeter of the fifth wheel preventing any inward movement of the operating handle thereby preventing slack adjustment necessitated by wear of the jaw and wedge. The 174 patent thus failed the basic feature embodied in the inventor's first U.S. Pat. No. 2,456,826, herein incorporated by reference, the embodiments of which have been practiced in the art for over 40 years and proven valuable in the trucking industry.
Like the "826" patent, a preferred embodiment of the current invention also permits adjustment for slack due to worn jaws and wedges. An additional advantage of the current invention is that because of the self-adjusting feature allowed by the ratchet system, a need to replace jaws and wedges is eliminated.
In the current invention stepped surfaces between the wedge and jaw are not necessary to decrease the slack caused by grease induced wear between the jaw and wedge. Instead a smooth surface between the jaw and wedge may be used allowing for less expensive manufacturing of such parts. Moreover, it does not matter whether grease becomes applied to the jaw and wedge. The inventor's experience has further proven that a smooth contact surface between the jaw and wedge will provide much better friction than stepped jaw and wedge contact surfaces when the contact surfaces are worn.
Further, it has been discovered by the inventor that application of the current invention provides for maintenance of narrower tolerances between king pin and jaw without the possibility of squirting. Additionally, the self-adjusting engagement of the wedge and jaw is able to be maintained in the closed position, which maintenance is benefited from the lever arm arrangement of the internal operating handle (lever arm) by both reducing the force applied to the detent and rack caused by the king pin and generating markedly tighter tolerances of movement between the jaw and wedge. Squirting and slippage is essentially eliminated, regardless of the presence of grease or worn components. Moreover, the design of the multi-positions (i.e. steps) of the self-adjusting ratchet system eliminates the human element involved in making sure the lever arm has fully closed and properly engaged the safety catch.
Integral to the advance in tightening tolerances of the current invention, a fully retractable pull handle is incorporated in association with the lever arm actuated detent and rack. There is a long felt need for this advancement in the art due to severe problems that have been caused by non-retractable type handles. As can be attested to by the presence of truck tire treads commonly found on the nation's highways, truckers have found that when the tractor is traveling without a trailer and the locking mechanism of the fifth wheel disengaged, since the non-retractable pull handle is extending over the tractor's tires, if a tire tread separates at high speeds, the centrifugal force of the tread slamming against the extended pull handle will often bend the shaft of the pull handle so that the locking mechanism is inoperative. Moreover, in many instances, if the shaft was improperly rebent to correct the damage done by the tire, the shaft was still not properly straightened leading to an inability of the locking mechanism to properly engage. Additionally, such non-retractable handles can be damaged by the trailer king pin if the tractor is backing into place improperly to engage the king pin into the fifth wheel. There have also been instances where the tires themselves of tractors equipped with air suspensions have bent an extended pull handle.
In a previous retractable handle design of the inventor in U.S. Pat. No. 4,946,183, the pull handle was able to retract only partially into the fifth wheel. The handle had a notch cut into one side of the handle shaft which acted as a safety catch and the slot allowing for retraction was L-shaped. In order for the handle to be retracted into the fifth wheel, the handle had to be manipulated laterally in order for the connecting bolt between the pull handle and operating handle to be slid along the slot in the pull handle for retraction of the pull handle when the operating handle was in the open position. This manipulation proved inconvenient. Moreover, since the pull handle did not fully retract, it was still subject to damage by separating tire treads. Also, the safety catch could fail to properly engage where the operating handle did not swing into a fully closed position.
In the current invention the retractable handle is able to fully retract whether the locking mechanism is open or closed and is not affected by type of tractor suspension, separating tire treads, or trailer king pins. Additionally, the slot is completely linear and not dependant upon any manipulation to retract. Moreover, there is no need for a safety notch because the ratch system acts as its own safety catch.
In association with the retractable handle yet another advance is incorporated in the current invention. Due to the design of the lever arm extending beyond the perimeter of the fifth wheel plate, the operator may visually tell from such visible portion, by the lateral or forward position of the lever arm extension, whether the locking mechanism is open or closed. Additionally, it is known that truckers often must operate their tractors during inclement weather conditions and at night. Moreover, all manufacturers specify in their operating instructions to examine the fifth wheel from behind (one even suggests using a flashlight if necessary) to determine whether the locking mechanism has actually locked. Such action by the operator is rarely carried out because to check the locked position of the fifth wheel from behind would require the driver to check the lock from under the trailer. Incorrect locking has been attributed to the most frequent cause of trailers becoming uncoupled over the past fifty years. Therefore, the current invention incorporates not only the extension of the lever arm to indicate whether the mechanism has locked but also includes as elements induction switches located so as to properly indicate whether the lever arm (thus, locking mechanism) is positioned in the open or closed position, and whether the trailer plate is resting or contacting the fifth wheel properly.
Prior inventions which have included electronic indicator switches include inventors U.S. Pat. No. 5,456,484 in which a button switch was placed so as to become depressed when the forward end of the wedge became seated in the locking position. However, the position of this switch negated the possibility of the wedge to adjust farther in the locked position as the wedge became worn thereby making any adjustment for slack impossible. Moreover, such switch was subject to malfunction due to grease buildup. Additionally a push button switch has been utilized in U.S. Pat. No. 3,535,679 wherein a lever arm having a hook lock mechanism would activate the switch when the lever arm was in a closed position. Unlike the present invention, the lever arm of the "679" design had only two positions of movement, open or closed. It could not adjust for wear induced slack. In contrast, the indicator switch of the present invention is able to activate when the lever arm is in the closed position while allowing for the lever arm to self adjust as needed. This advance is due to the use of an electronic switch in the form of an induction switch. Likewise, the ability to detect whether the trailer plate is resting or contacting the fifth wheel properly is also allowed by an induction switch.
Yet another embodiment of the invention incorporates a means by which a fifth wheel may support a trailer via the trailer riding plate without the use of a grease-based lubricant and further without the mating surfaces of the trailer plate and fifth wheel binding. Specifically, the current invention solves the long felt need recognized since the early days of the industry for a means to create a non-binding surface between the trailer plate and fifth wheel without a need for grease. The use of grease as a lubricant has always been the means for creating non-binding surfaces between the trailer and fifth wheel. However, the presence of grease has always presenting a great deal of handling problems for the operator. For example, when a fifth wheel required repair, the grease made for exceptionally messy work environments in the repair shop. Moreover, not only does the grease seep into the locking mechanism elements thereby facilitating wearing and squirting, the grease also attracts road grit which gums up the locking mechanism components and in frigid environments of winter months, the grease will solidify sometimes freezing causing the locking elements to become inoperative. The cost of grease and labor to install is eliminated. The tractor becomes much easier to clean and stays clean longer. Weight is also reduced because there is no mud and dirt which are normally attracted by grease.
The current invention has solved the grease problem by incorporating into the fifth wheel plate materials having properties of a low coefficient of friction, high density, low compressibility, and high impact resistance. Such material is recessed into the top plate in the form of a plurality of strips which are embedded deep enough in the top plate to protect such strips from damage or distortion especially when the trailer plate slides on the fifth wheel during coupling. The strips are further raised 1/16th to 1/8th inch above the surface of the fifth wheel plate so as to keep the trailer plate from contacting the fifth wheel plate.
The strips out perform and operate in a functionally different manner than other grease avoiding component designs because of the unique spacing and manner of incorporation. In other inventions such as disclosed in U.S. Pat. Nos. 3,924,909, 4,169,635, 4,752,081, 5,165,714, 5,263,856, and 5,431,424 a high molecular weight polyester material and other composite materials were either bonded, welded, or bolted to the surface of the fifth wheel top plate. Moreover, such prior designs required a substantial surface of the fifth wheel plate to be covered by such materials. Some designs comprised whole sheets of the plastic material covering the entire plate while others comprised large plastic plates. Practical use of such designs has proven unsatisfactory in the long run due to abrasive or disruptive action of the trailer plate scraping across the surface of the fifth wheel when coupling. For example, the use of plastic sheeting failed due to wrinkling, dislodging, or ripping of the plastic from its intended position. The current invention provides a unique means of providing for protection by inserting the low friction composite material within depressions incorporated directly into the surface of the fifth wheel plate. Moreover, the low friction material of the current invention requires that only narrow strips of material be used such that the strips rise above the surface of the metal plate by only 1/16th to 1/8th inch. Thus, the over all profile of the fifth wheel plate is lower that other greaseless designs. The capacity for utility with such narrow bands of material is provided by the fact that the material applied in the current invention has a lower coefficient of friction and higher impact resistance that used in prior methods.